/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.truth.Truth.assertThat;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertFalse;
import static junit.framework.Assert.assertTrue;
import static junit.framework.Assert.fail;

import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nullable;

/**
 * Used to test listenable future implementations.
 *
 * @author Sven Mawson
 */
public class ListenableFutureTester {

    private final ExecutorService exec;
    private final ListenableFuture<?> future;
    private final CountDownLatch latch;

    public ListenableFutureTester(ListenableFuture<?> future) {
        this.exec = Executors.newCachedThreadPool();
        this.future = checkNotNull(future);
        this.latch = new CountDownLatch(1);
    }

    public void setUp() {
        future.addListener(new Runnable() {
            @Override
            public void run() {
                latch.countDown();
            }
        }, exec);

        assertEquals(1, latch.getCount());
        assertFalse(future.isDone());
        assertFalse(future.isCancelled());
    }

    public void tearDown() {
        exec.shutdown();
    }

    public void testCompletedFuture(@Nullable Object expectedValue) throws InterruptedException, ExecutionException {
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        assertEquals(expectedValue, future.get());
    }

    public void testCancelledFuture() throws InterruptedException, ExecutionException {
        assertTrue(future.isDone());
        assertTrue(future.isCancelled());

        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertTrue(future.isDone());
        assertTrue(future.isCancelled());

        try {
            future.get();
            fail("Future should throw CancellationException on cancel.");
        } catch (CancellationException expected) {
        }
    }

    public void testFailedFuture(@Nullable String message) throws InterruptedException {
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        try {
            future.get();
            fail("Future should rethrow the exception.");
        } catch (ExecutionException e) {
            assertThat(e.getCause()).hasMessage(message);
        }
    }
}
